Sash Balance Calculator: Find Your Balance Type and Size
Sash balance calculator type and size selector
Spring sash balances are made to order to suit your exact window. We fit UNIQUE Sash Balances, made right here in Australia to a trade grade standard rather than shipped in as a generic import. Enter three measurements and this selector gives the balance type, the product numbers for both sashes and the quantities, ready to order.
Your window
A is the overall height: inside top of the head down to the inside bottom of the sill.
The calculator estimates the bottom sash weight from your measurements, the same physics as our lead weight calculator. If the sash has actually been on scales, enter that figure and it wins.
Horns are the small downward extensions on the top sash stiles. With 50mm horns the top sash takes the same balance as its own height row. Another horn size needs checking with us before ordering.
How the selection works
The overall height (A) sets the balance product number from the maker's fitment chart, numbers 10 through 48. The rebate groove sets the type: Type A takes a 10mm tube, Types B and HD take a 13.4mm tube, Type D takes a 14.5mm tube. The sash weight confirms the spring: Type A carries to 8.16kg, Type D to 13.6kg, Type B to 14kg and Type HD to 18kg.
The sash weight is estimated from the width, glazing and timber, taking each sash as half the overall height, or from the individual sash heights when the sashes are unequal. Glass is 2.5kg per square metre for every millimetre of thickness, timber is figured at standard Australian sections, and glazing bars add about 10 percent. A weighed figure always beats the estimate, which is why the optional field wins when filled in.
The bottom sash takes the number matched to the height, and the top sash takes a balance two sizes shorter, unless it has 50mm horns, in which case it matches. When the sashes are unequal, each sash is simply sized off its own height, so the top and bottom order different numbers.
Balance type
Your order
All sizes are currently out of stock. This opens an email with your numbers filled in so we can notify you the moment your size is back.
UNIQUE Sash Balances — designed and made in Australia, built to order for your window.
Cords and weights still in the frame? If your window has its original pockets, rebalancing with lead weights is usually simpler and cheaper than converting to balances, and those are in stock now. Balances suit windows built without weight pockets, or frames where the pockets are gone.
What a sash balance is
A sash balance is a spring inside an aluminium tube that does the job cast iron weights do in a traditional box frame. One balance fits each side of each sash, the tube screwed to the frame and the foot screwed under the sash. Many newer double hung windows were built with balances instead of weight pockets, and when the springs tire the sash drops or refuses to stay up.
We fit UNIQUE Sash Balances — designed and manufactured in Australia, not a generic import off a container. Every balance is built to order for your window's exact height and weight rather than sold as a one-size-fits-most part, with a spring mechanism and materials made to keep doing the job for years, not just get a sash through its first winter. It's the balance we'd put in our own windows, which is why it's the one we supply. Read more on why we only fit UNIQUE and not a cheap import.
Because each one is made for the window, they take a minimum of 10 business days before dispatch and cannot be returned or refunded once ordered. The selector above exists so the number you order is the right one, the first time. All sizes are currently out of stock — use the selector to confirm your spec and join the waitlist for your size.
The four balance types
| Type | Tube diameter | Rebate groove | Carries a sash up to |
|---|---|---|---|
| Type A | 10mm | 11mm x 11mm | 8.16kg |
| Type B | 13.4mm | 14 to 15mm | 14kg |
| Type D | 14.5mm | 16mm x 16mm | 13.6kg |
| Type HD | 13.4mm | 14 to 15mm | 18kg (heavy duty) |
The rebate groove in the sash stile decides which tube fits, and the sash weight decides whether the standard spring in that type will carry it. A heavy sash in an 11mm rebate is the awkward case: Type A tops out at 8.16kg, so the groove may need recutting for a bigger tube. Ring us before ordering if that is your window.
How to measure for sash balances
Three measurements, all taken with the window shut:
1. Overall height (A). Inside top of the head to the inside bottom of the sill, in millimetres. This single figure sets the balance product number. If the two sashes are not the same size, measure each sash height along its stile as well.
2. Sash width and glazing. The calculator estimates the sash weight from the width, the glass and the timber, so there is no need to pull the sash out and find bathroom scales. The maker uses the weight to confirm the spring size, and if you do happen to have a weighed figure, enter it in the optional field and it takes over from the estimate.
3. Rebate groove. Measure the groove in the sash stile that the tube sits in, or measure the diameter of the old balance tube.
Also note what foot your existing balances have (the fitting that attaches under the sash) so the replacement matches. If you are unsure, a photo of the old balance and its foot sent with your order sorts it.
Balance selection chart
The full fitment chart, as used by the selector above. Find the range your overall height (A) falls in; that row is the bottom sash balance. The top sash takes the number two sizes smaller, or the same number if it has 50mm horns. For example, a 1250mm window takes a number 22 on the bottom sash and a number 20 on top. Unequal sashes size each sash off its own height instead.
| Window height A (mm) | Balance no. | Tube (mm) | Closed (mm) | Open (mm) |
|---|
Frequently asked questions
Are sash balances in stock? Not currently. You can still use the calculator to find your exact type and numbers, and send us your spec to join the waitlist for that size.
Why UNIQUE Sash Balances rather than a cheaper import? They're designed and made in Australia to a trade standard, and built to order for your window rather than sold as a generic off-the-shelf part. It costs more than a mass-produced import, but it's the balance we're prepared to put our name behind, and the one that's still doing its job years after a cheaper part would have given up.
How do I know what size sash balance I need? Measure the overall window height from inside the head to inside the sill. That height maps to a balance product number on the chart above, with the top sash two sizes smaller unless it has 50mm horns.
How many balances does one window need? Four: two on the bottom sash and two on the top sash, one each side.
Do I have to weigh the sash? No. The calculator estimates the weight from the sash width, glazing and timber. A weighed figure is still the gold standard, and there is an optional field for it that overrides the estimate.
What if my sash is heavier than the type allows? Type HD carries up to 18kg in a 14 to 15mm rebate. Heavier than that, or a heavy sash in a small rebate, needs a conversation before ordering.
Balances or weights and cords? If the frame has its weight pockets, lead weights are usually the simpler fix and can be ordered off the shelf. Balances are for windows built without pockets or where the pockets have been built over.
Why are balances non-returnable? Each one is made to order for your measurements. That is also why they take a minimum of 10 business days before dispatch.
My sashes are different sizes. Tell the calculator: switch the sashes question to No and enter each sash height along its stile. Each sash gets the balance size matched to its own height, so you simply order a different number for the top than the bottom. The spring is checked against the heavier sash and both heights travel with the order email.